The present invention relates to a method for making corrosion resistant metallic objects having thin walls. The method is particularly useful for making small diameter stainless steel tubing for use in corrosive heat exchange environments and for making stainless steel structural honeycomb material.
Metallic heat exchangers having a large number of fluid passageways are in common use, for example in air conditioning systems, heat pumps and external combustion engines. A common problem with such heat exchangers is that the working fluid inside the heat exchanger and the environment outside the heat exchanger are often corrosive. After the heat exchanger has been in operation for a long period of time, the action of corrosive fluids on the metal of the heat exchanger may decrease the efficiency at which heat is transferred through the metal and may even cause leaks or blockages.
Corrosion resistant metals, such as stainless steel, may be used for such heat exchangers to avoid corrosion or to reduce the rate of corrosion. Unfortunately, however, most corrosion resistant materials do not conduct heat as efficiently as the corrodible metals that they would be replacing. Thus, production of an efficient heat exchanger using a corrosion resistant metal requires the use of fluid passageways having very thin walls. It is often expensive and difficult to produce stainless steel objects having very small passageways or very thin walls using currently known methods, particularly since stainless steel tends to crack when it is worked.
The primary object of the present invention is to provide an inexpensive method for producing corrosion resistant metallic objects having thin walls. A second object of the present invention is to provide a method of producing stainless steel tubing. A third object of the present invention is to provide a method to produce in a continuous process a large quantity of small diameter tubing having thin walls. Another object of the present invention is to provide an inexpensive method for producing stainless steel heat wheels having numerous small diameter passageways of a predetermined uniform small diameter. Still another object of the present invention is to provide a method of producing light weight stainless steel honeycomb material.